1899] MICROSCOPICAL JOURNAL 273 



with streptococci and other micro-organisms, is of great 

 interest because of the increased danger to life, and be- 

 cause it may serve to explain at times the failure of the 

 antitoxin which does not protect against other toxins 

 than that of diphtheria. But these are points of interest 

 to the practicing physician rather than the microscopist. 



The fact that the diphtheria, like many other diseases, 

 spreads in waves over extensive portions of the earth's 

 surface, increasing very largely for a year or two, and 

 then subsiding for a series of years, is usually referred 

 to meteorological conditions modifying the virulence of 

 the bacillus itself, or modifying the conditions on which 

 its virulence depends. It may, however, be a question 

 for study by the methods of modern microscopy. It is 

 possible that the products of the bacterial activity may 

 inhibit the growth of these organisms, in and out of the 

 body, on a scale large enough to be evident at a glance in 

 the statistics showing their epidemic prevalence. In other 

 words even when practically left to themselves, as is the 

 rule in many parts of the world, they do not increase in- 

 definitely but exhaust the material susceptible to their 

 attack, and perhaps in a measure originate their own an- 

 titoxines. In either case it is a question to be determ- 

 ined by the culture methods of the bacteriologist and 

 microscopist, identifying atypical and modified forms of 

 the bacillus, and their relation to the severity of the dis- 

 ease in particular cases, and its epidemic prevalence in 

 general. 



Another exceedingly interesting series of questions is 

 as to why the bacillus attacks children in preference to 

 adults, and certain tissues and parts of the body in pref- 

 erence to others. Considerable light has been thrown 

 upon these very difficult and obscure phases of the sub- 

 ject by modern methods of study of embryology and 

 comparative anatomy, bringing out what may be termed 

 the developmental relations involved. This is the 



